I know I'm the Community Rep for NZXT, so some may find what I say to be biased, but, I've owned over 20 other cases in the last 5 years from just about every company out there, so here goes:

Pros:
Awesome Watercooling support
Fan Controller
Build quality (the plastics are tough, the steel is tough, very solid and can be moved around easily as long as you have muscles)
Hue and Lots of stylistic LED placement

Cons:
Mesh instead of acrylic on the side panel (I modded mine so that there are acrylic windows on all 3 spots.)
Drive trays ARE flimsy, but they work well when you get a drive installed.
Front only supports 200mm fans. bleh!

If you're having trouble deciding, maybe the 630 would be more to your liking? I think the 2 SSD trays on the mobo tray almost alone makes it better than the 820. They have pros and cons to each. Just have to pick which suits your wants/needs.